/*
 * =========================================================================================
 * Copyright © 2013-2015 the kamon project <http://kamon.io/>
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the
 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 * =========================================================================================
 */
package kamon.util

import java.util.function.Supplier

import kamon.trace.{SpanContext => KamonSpanContext}
import kamon.Kamon
import org.slf4j.MDC

import scala.collection.JavaConverters._

object BaggageOnMDC {

  /**
    * Copy all baggage keys into SLF4J's MDC, evaluates the provided piece of code and removes the baggage keys
    * afterwards, only when there is a currently active span. Optionally adds the Trace ID as well.
    *
    */
  def withBaggageOnMDC[T](includeTraceID: Boolean, code: => T): T = {
    val activeSpan = Kamon.activeSpan()
    if(activeSpan == null)
      code
    else {
      val baggageItems = activeSpan.context().baggageItems().asScala
      baggageItems.foreach(entry => MDC.put(entry.getKey, entry.getValue))
      if(includeTraceID)
        addTraceIDToMDC(activeSpan.context())

      val evaluatedCode = code

      baggageItems.foreach(entry => MDC.remove(entry.getKey))
      if(includeTraceID)
        removeTraceIDFromMDC()

      evaluatedCode

    }
  }

  def withBaggageOnMDC[T](code: Supplier[T]): T =
    withBaggageOnMDC(true, code.get())

  def withBaggageOnMDC[T](includeTraceID: Boolean, code: Supplier[T]): T =
    withBaggageOnMDC(includeTraceID, code.get())

  def withBaggageOnMDC[T](code: => T): T =
    withBaggageOnMDC(true, code)

  private val TraceIDKey = "trace_id"

  private def addTraceIDToMDC(context: io.opentracing.SpanContext): Unit = context match {
    case ctx: KamonSpanContext => MDC.put(TraceIDKey, HexCodec.toLowerHex(ctx.traceID))
    case _ =>
  }

  private def removeTraceIDFromMDC(): Unit =
    MDC.remove(TraceIDKey)
}